Dear EarthTalk: What is the deal with plastics recycling these days? Can you explain what the different numbers molded onto the bottom of plastic containers stand for?

—Tom Croarkin, Fairfield, CT

The confusion over what we can and cannot recycle continues to confound consumers. Plastics are especially troublesome, as different forms of plastic require differing processing in order to be reformulated and re-used as raw material. Some municipalities accept all types of plastic for recycling, while others only accept jugs, containers and bottles with certain numbers stamped on their bottoms.

The symbol code we’re familiar with—a single digit ranging from "1" to "7" surrounded by a triangle of arrows—was designed by The Society of the Plastics Industry (SPI) in 1988 to allow consumers and recyclers to differentiate types of plastics while providing a uniform coding system for manufacturers.

The numbers, which 39 states now require be molded or imprinted on all eight-ounce to five-gallon containers that can accept the ½” minimum size symbol, identify the type of plastic and, according to the American Plastics Council, an industry trade group, help recyclers do their jobs more effectively.

The easiest and most common plastics to recycle are made of polyethylene terephthalate (PETE or PET) and are assigned a "1." Examples include soda and water bottles, medicine containers and many other common consumer product containers. Once it has been processed by a recycling facility, PETE can become fiberfill for winter coats, sleeping bags and life jackets. It can also be used to make bean bags, rope, car bumpers, tennis ball felt, combs, cassette tapes, sails for boats, furniture—and, of course, other bottles.

Number "2" is reserved for high-density polyethylene plastics. These include those heavier containers that hold laundry detergents and bleaches as well as milk, shampoos and motor oils. Plastic #2 is often recycled into toys, piping, plastic lumber and rope. Like #1 plastic, it is widely accepted at recycling centers.

Polyvinyl chloride, commonly used in plastic pipes, shower curtains, medical tubing, vinyl dashboards—even some baby bottle nipples—gets number "3." Like numbers "4" (wrapping films, grocery and sandwich bags and other containers made of low-density polyethylene) and "5" (polypropylene containers used in Tupperware, among other products), few municipal recycling centers will accept it due to its very low rate of recyclability. Number "6" goes on polystyrene (Styrofoam) items such as coffee cups, disposable cutlery, meat trays, packing "peanuts" and insulation, and is widely accepted because it can be reprocessed into many items including cassette tapes and rigid foam insulation.

Last but far from least are items crafted from various combinations of the aforementioned plastics or from unique plastic formulations not commonly used. Usually imprinted with a "7" or nothing at all, these plastics are the most difficult to recycle and, as such, are seldom collected or recycled. More ambitious consumers can feel free to return such items to the product manufacturers to avoid contributing to the local waste stream and instead put the burden on the makers to recycle or dispose of the items properly.

The best way to deal with problem bears is to prevent human-bear encounters in the first place. As human population has grown and people have encroached more and more on forested areas, bears have been forced to share what has traditionally been their domain with more and more of us.

Mostly what attracts bears is food. When people don’t dispose of food wastes properly, whether at campsites or at home, bears follow the smell and come calling. And once bears get a taste for human food scraps they will return time and again for more, increasing the chance of conflicts. Game managers at the mercy of a frightened public are left with little choice but to shoot the unwitting creatures.

But bears don’t have to die in order to resolve such conflicts. The most common alternative to the death sentence for bears is relocation. However, says Allison Jones of the non-profit Wild Utah Project, "the efficacy of this method is still debated." She cites one study that found 81 percent of bears returning that were relocated 40 miles away or less, and 48 percent returning of those relocated 40 to 75 miles away.

One non-lethal tactic for keeping bears away was developed by the Florence, Montana-based Wind River Bear Institute (WRBI). According to WRBI founder and bear biologist Carrie Hunt, the group’s "bear shepherding" strategy involves trapping and then releasing a bear at the site of its "crime." As the bear is released from its cage, it is shot with red pepper spray and rubber bullets. Hunt’s trained Karelian bear dogs then chase the bear, scaring it so much that it chooses not to return. While this may not seem so humane, it has succeeded in sparing the life of many a wayward bear while keeping it permanently away.

Short of such war-like tactics, WRBI’s website provides tips for homeowners on keeping bears from wandering onto property, including: packing away barbecue grills and all food scraps after meals are over; limiting compost piles to grass, leaves and garden clippings (i.e. no food); feeding pets indoors instead of outside; eliminating bird feeders and replacing hummingbird feeders with hanging flower baskets that will still attract the birds but not bears; and picking fruit from fruit trees as soon as it is ripe while also removing rotting fallen fruit from the ground.

Meanwhile, park rangers at Yosemite National Park report that human-bear encounters have decreased significantly there since they mounted an aggressive campaign to educate park visitors about bear safety. "By far, the most effective technique we’ve used is education—letting people know that their behavior, especially in regard to food storage, plays a huge role in attracting bears," says Adrienne Freeman, a Yosemite park ranger. "Bears are not the problem; people are the problem," she says.

The campaign seems to be working. Back in 1998, rangers reported that bears carried out $630,000 worth of property damage in more than 1,000 incidents with the park’s human visitors. But by late 2005, bears had only caused $84,000 in property damage, and the number of incidents was down 75 percent from 1998.